Electrostrictive display means



Feb. 1, 1966 P. J. CRANE ELECTROSTRICTIVE DISPLAY MEANS Filed Jan. 2, 1962 mdv wa QNQS KO MQQQQW United States Patent 3,233,040 ELECTROSTRICTIVE DISPLAY MEANS Paul J. Crane, Torrance, Calif., assignor to The Magnavox Company, Torrance, (Ialif, a corporation of Delaware Filed Jan. 2, 1962, Ser. No. 163,768 9 Claims. ((31. 178-75) The present invention relates to display means and, more particularly, to a means for projecting an enlarged image upon a screen.

At the present time it is very desirable to be capable of instantaneously producing visual images for display purposes. For example, it may be desirable to create a picture of certain objects or persons, maps, radar presentations, etc., at the very instant that the particular condition exists whereby several persons may simultaneously view the display. One means of accomplishing this is to employ a cathode ray type of vacuum tube. In such a tube one end of the tube has a display or image area that is coated with a layer of phosphorescent material. The opposite end of the tube includes an electron gun for directing a stream of electrons onto the phosphorescent surface whereby the phosphorus therein will glow and form a luminous image. Although very good, high quality images can be created in this manner, the physical size of a cathode ray tube is severely limited and as a result the sizes of the images created are correspondingly limited. Although there are numerous schemes for optically enlarging the image to greater proportions, all of the light for the image has heretofore been obtained from the cathode ray tube. Since the light available from a cathode ray tube is very limited, the quality of the image and particularly the brightness thereof rapidly decreases as the size thereof increases. Accordingly, heretofore it has been extremely difflcult, if not impossible, to instantly create large size images of high quality and brightness.

It is now proposed to overcome the foregoing difliculties and provide display system for producing high quality images of virtually unlimited size and brightness. More particularly, it is proposed to provide an optical surface and means for electronically altering said surface in patterns corresponding to the images to be created. The optical surface may be formed on a piezoelectric or electrostrictive member whereby it will be possible to produce distortions in the surface corresponding to the image so as to permit an enlarged image to be projected onto a screen. In the present instance, this is to be accomplished by providing a layer of piezoelectric or electrostrictive material on the target end of a cathode ray vacuum tube. The exterior surface of the layer forms an optically smooth reflecting surface that is substantially a plane. The interior of the surface layer is interconnected with the interior of the tube so that the layer may acquire an electrical charge from an electron beam scanning the interior of the target end of the tube. An external source of illumination may then project light onto the normally plane reflecting surface of the piezoelectric or electrostrictive layer whereby light will be reflected from the surface.

An optical system such as of the Schlieren variety may be provided which will direct the reflected light normally reflected from the plane reflecting surface onto a mask. However, the light reflected from the surface distortions in the piezoelectric or electrostrictive layer may be projected onto a screen. Thus, an enlarged image may be projected onto a screen so as to correspond to the distortion-producing electrical charge pattern laid down by the electron beam. Since the source of illumination for the projected image is external to the cathode ray tube, the image may be enlarged to virtually any desired size Without the brightness thereof decreasing by increasing the light source.

These and other features and advantages of the present invention will become readily apparent from reading the following detailed description of one embodiment of the invention particularly when taken in connection with the drawings wherein like reference numerals refer to like parts and wherein:

FIGURE 1 is a diagrammatic showing of one embodiment of the present invention; and

FIGURE 2 is a transverse cross-sectional view on a highly enlarged scale of that portion of FIGURE 1 enclosed in the dotted circle.

Referring to the drawings in more detail, the present invention is particularly adapted to be embodied in a display system 10 for projecting an enlarged image onto a screen 12. This screen 12 is preferably of adequate dimensions to accommodate an image of the required size.

In order to enlarge and project an image onto the screen 12, a suitable optical system 14 is provided. Although this optical system 14 may be of any suitable variety, in the present instance it includes an optical member 15 and a lens system 18.

The optical member 15 may be of any suitable variety that may be readily distorted into different shapes. In the present instance this member 15 includes a layer 24 of a suitable electrostrictive material. One side of this layer 24 may form an optical conductive surface 26 which is preferably substantially a plane. The surface 26 is preferably polished or otherwise sufliciently smooth to form an efilcient reflector and electrode. More particularly, the surface is preferably normally sufliciently smooth and flat to cause a collimated beam of light projected thereon to be reflected as a second collimated beam of light. However, in the event there is an electrical charge on some portion of the layer that causes that portion of the surface 26 to be distorted from the plane, the light reflected from the distortions will not be parallel to the reflected beam.

The lens system 18 may be of any suitable variety but in the present instance is of the so-called Schlieren variety. It includes a point source of light 28 and a first lens 36 for focusing the light from the source 28 into a collimated beam 32 of light rays 34. This beam 32 is aimed so as to be projected substantially uniformly onto the surface 26 of the electrostrictive layer 24. Since the surface 26 is normally a plane, the light incident thereon will be reflected therefrom in the form of a collimated beam 36 of light rays 38.

A second lens 42 may be provided which is disposed in the reflected beam 36 so as to focus all of the parallel rays 38 into a focal point. A small opaque mask 44 may be disposed at the focal point of this second lens 42. It is, of course, readily apparent that the collimated light in the reflected beam 36 will be focused toward the focal point by the lens 42. Since the mask is disposed at this point, the light will be concentrated on the mask and blocked from traveling therepast.

A third lens 46 may be disposed behind the mask 44 and in substantial alignment with the reflected beam 36. The combination of the second and third lenses 42 and 46 are preferably focused upon the surface of the piezoelectric or electrostrictive layer 24 whereby an image corresponding to the pattern on the surface 26 will be projected onto the screen 12. It may thus be seen that the light from the point source 28 will be collimated into a beam 32 that will normally be reflected from the plane surface 26 in the form of the collimated beam 36. The rays 38 in this beam 36 will be focused onto the mask 44 so as to be completely blocked thereby. As a result,

3 virtually none of this light will be reflected onto the screen 12.

However, in the event there are one or more distortions 74 in the surface 26 which extend above or below the plane thereof, the light reflected therefrom will include light rays 48 which are skew to the axis of the reflected beam 36. These light rays 48 will pass through the second lens 42 but will not be focused onto the mask 44. However, they will pass the mask 44 and because of their skewness the lenses 42 and 4-6 will focus them onto the screen 12. Accordingly, an image will be projected onto the screen so as to correspond to the pattern of the distortions of the surface 26.

In order to form the distortions in the surface 26 of the piezoelectric electrostrictive layer 24, an electrical charge pattern may be created'thereon. Although this can be accomplished in any suitable manner, in the present instance a cathode ray vacuum tube 5% is employed so that an electron gun may direct a stream 52 of electrons so as to create the charge pattern on the layers 24. More particularly, the cathode ray tube 56 includes an airtight envelope 54 which includes a cylindrical portion 56, an end wall 58 and a tapered portion 60 which extends therebetween. The cylindrical portion 56 encloses a conventional electron gun 57 which is adapted to direct a stream 52 of electrons axially of the tube 5 toward the opposite end thereof. This gun may include suitable deflection means 59a and 59b for controlling the intensity and direction of the stream whereby a suitable video system 62 may be connected to the gun for causing the stream to scan the opposite end of the tube.

The opposite end of the tube includes the end wall 58 which forms a target area against which the stream 52 of electrons may be directed. This end wall 58 preferably consists of a dielectric material such as glass so as to be a poor conductor of electrons. As a result, electrons striking the end wall 58 will not be immediately dissipated but instead may cause substantial electrical charges to be accumulated in localized spots. The layer 24 of electrostrictive material that is disposed on the outside of the end wall is preferably comparatively thin and uniformly distributed over the end wall and consists of an elec trostrictive material which will change its shape in response to the electrical charge thereon. The end wall 58 is preferably substantially a plane whereby the outside surface 26 of the electrostrictive layer 24 will also be a plane. This surface 26 is preferably optically smooth and normally sufliciently plane to insure a beam 32 of collimated light rays 34 incident thereon to be reflected therefrom as a second beam 36 of collimated light rays 38.

In order to permit the charges of electrons created on the inside of the end wall 58 to be distributed to the piezoelectric or electrostrictive layer 24, a matrix of elec trical conductors may be provided which extends through the end wall 58. In the present instance these conductors consist of a large number of closely spaced fine wires ill that are disposed transversely of the end wall 58. The inner ends of these wires '70 may include electrical contacts 72 such as enlarged beads of silver. The outer ends of the wires 79 extend through end wall 58 and come into intimate electrical contact with the electrostrictive layer 24. Accordingly, if a stream 52 of electrons is directed toward the end wall 58 they will be incident upon the enlarged beads 72. This, in turn, will cause an electrical charge to be carried over the wires 70 to the piezoelectric or electrostrictive material. Since the end wall 58 and electrostrictive layer 24 are poor electrical conductors, the video system 62; may cause the stream 52 of electrons to create any desired charge pattern on the piezoelectric or electrostrictive layer 24 whereby the surface 26 of the layer 24 will be distorted in a corresponding pattern by means of the electric field between wire ends '70 and electrode 26.

It may thus be seen that in order to employ the present embodiment of the invention, to project an enlarged image onto the screen 12 the point source 28 of light is turned on. The first and second lenses 3d and 42 are then adjusted so that a collimated beam 32 of light will be directed onto the surface 26 and reflected therefrom in a collimated beam 36 which will be focused onto the mask 44 whereby the reflected light will be blocked from reaching the screen i2. Following this, the video system or source of video signals 62; may be turned on and supplied with a suitable video signal corresponding to the image that it is desired to create. The stream 52 of electrons may then scan across the target area formed by the end wall 53 and the electrical contacts '72. This, in turn, will cause an electrical charge pattern to be distributed across the electrical beads 72. The matrix of conductors 743 will immediately carry the charge through the end wall 58 to tl e layer 24 of piezoelectric or electrostrictive material. Thus, the layer 24 of electrostrictive material will acquire a corresponding charge pattern. The thickness of the piezoelectric or electrostrictive material will then be changed in accordance with the distribution of the electrical charge pattern thereon. As a consequence, the plane surface on the exterior of the layer 24 of piezoelectric or electrostrictive material will be distorted out of the plane to form a pattern of depressions and/or projections '74. The collimated light in the beam 32 from the point source 28 incident of the reflected surface 26 will be reflected toward the second and third lenses E2 and 46. The light rays 33 reflected from those portions of the surface 26, which are still in the plane, will still be in substantially parallel relationship. As a result, the second lens 42 will cause this light to be focused onto the mask 44 and blocked from traveling therepast to the screen 12. However, the light rays 48 reflected from those portions '74 of the surface 26 which are distorted out of the plane by the electrical charge thereat will be skew to the axis of the reflected beam 36. Since these light rays 48 do not travel parallel to the axis of the beam 36, the second lens 42 will not focus them onto the mask 44. As a consequence, when these light rays 48 pass through the third lens 46 they will be focused onto the screen 12 to thereby form an image.

It may thus be seen that the video system 62 may be effective to cause a charge pattern to be distributed on the layer 24 of the piezoelectric or electrostrictive material. This, in turn, will cause the surface 2e to be piezoelectrictively or electrostrictively distorted to form a pattern corresponding to the image to be created. The lens system 18 will then cause the light reflected from these distortions to be projected onto the screen 12,. Accordingly, it is now possible to instantly project an enlarged image onto the screen 12 and the size thereof may be greatly enlarged over the size of an image that can be created by a cathode ray tube. In addition, since the light for this image is supplied from a point source disposed externally to the cathode ray tube, this light may be made as bright as desired. Accordingly, even through the image is greatly enlarged, it may be still be made as bright as desired.

It may thus be seen that a display system 10 has been provided for instantly projecting enlarged images onto a screen 12. Although only a sin le embodiment of the invention has been disclosed, it will be readily apparent to persons skilled in the art that numerous changes and modifications may be made thereto without departing from the spirit of the invention. Accordingly, the foregoing disclosure and description thereof are for illustrative purposes only and are not to limit the invention which is to be defined only by the claims which follow.

What is claimed. is:

1. A cathode ray tube comprising the combination of an envelope having a dielectric end wall adjacent one end thereof, an electron gun disposed adjacent the opposite end of said envelope for directing a stream of electrons toward the inside surface of said end wall, electrostrictive means disposed. on the outside surface of said end wall to form an optical surface and means for conducting an electrical charge from said inside surface of said end wall to said electrostrictive means thereby causing the shape of said surface to change.

2. A cathode ray tube comprising the combination of an envelope having a dielectric end wall adjacent one end thereof, an electron gun disposed adjacent the opposite end of said envelope for directing a stream of electrons toward the inside surface of said end wall, a layer of electrostrictive material disposed on the outside of said end wall, the exterior of said layer forming an optically smooth reflecting surface, and a plurality of electrically conductive means extending between said inside and said outside surfaces of said end Wall so the charge produced by said stream of electrons may be carried to said electrostrictive means to thereby cause the shape of said reflective surface to be changed.

3. A cathode ray tube comprising the combination of an envelope having a plane dielectric end wall adjacent one end of said envelope, an electron gun disposed adjacent the opposite end of said envelope for directing a 'stream of electrons toward said end wall, a layer of electrostrictive material disposed on the exterior of said end wall, said layer forming a normally plane optical reflecting surface, and a mosaic of electrically conductive members extending through said end wall for carrying the charge deposited on said inside surface thereof by said stream to the outside surface thereof whereby said layer will acquire an electrical charge and will change the shape of the surface thereof in response to said electron stream.

4. In combination for use with a source of video signals for creating an optical image suitable for being illuminated from an external light source and for being projected onto an enlarged viewing surface of a projection screen.

an air tight envelope defining a volume having a vacuum therein,

an end wall on one end of said envelope for forming a target area, said end wall being formed from a dielectric material for accumulating an electron charge thereon,

an electron gun disposed at the opposite end of said envelope for directing a beam of electrons toward said end wall,

deflection means in said electron gun and responsive to the video signals from the source for scanning said electron beam across said end wall to form on said end wall a raster containing an electron charge pattern corresponding to said optical image,

a layer of substantially uniform thickness disposed on said. end wall and having at least one optical surface for reflecting light therefrom, said layer consisting of an electrostrictive material responsive to the charge thereon for changing its thickness to create deformations in the surface corresponding to the charge thereon,

means disposed in cooperative relationship with the end wall and the layer of electrostrictive material for transferring said charge pattern onto said layer from said end wall for deforming said optical surface to produce a visual image in response to said charge pattern,

means disposed relative to the light source for directing light from the source to the layer of electrostrictive material to obtain a reflection of such light from the layer in accordance with the deformations in the layer, and

means responsive to the light reflected from the layer of electrostrictive material for producing an image in accordance with the characteristics of the deformed light.

5. In combination for use with a source of video signals for creating an optical image suitable for being illuminated from an external light source and for being projected onto an enlarged viewing surface of a projection screen,

an air tight envelope defining a volume having a vacuum therein,

an end wall on one end of said envelope for forming a target area, said end wall being formed from a dielectric material for accumulating an electron charge thereon,

an electron gun disposed at the opposite end of said envelope for directing a beam of electrons across said volume and toward said target area,

deflection means in said electron gun and interconnected with said source of video signals for modulating and scanning said electron beam across said target area in response to said video signals to form a raster containing an electron charge pattern corresponding to said optical image,

a layer of electrostrictive material disposed on said end wall at the end opposite to the electron gun, said layer normally having a substantially uniform thickness and forming at least one optical surface for reflecting light therefrom, said electrostrictive material being responsive to the charge thereon for changing its thickness to create deformations in said surface corresponding to said charge,

means operatively coupled to the end wall and the layer for transferring said charge pattern from the end wall onto said layer to thereby cause said optical surface to be deformed similar to said charge pattern,

means optically coupled to the light source for directing light from the source to the optical layer to obtain a reflection of light from the layer of electrostrictive material in accordance with the deformations in the optical surface, and

means responsive to the light reflected from the optical surface for providing a visual image in accordance with the characteristics of the deformed light reflected from the optical surface.

6. Projection means for projecting an enlarged optical image onto a projection screen, including:

a projection screen having a surface for displaying a visual image,

a cathode ray tube having an envelope that defines a volume having a vacuum therein,

an end wall on one end of said envelope to form a target area, the end wall being formed of a dielectric material for accumulating a charge on the end wall,

an electron gun disposed at the opposite end of said envelope for directing a beam of electrons across said volume toward said target area to scan said area and create an electron charge on said target area,

means operatively interconnected with said electron gun for modulating the intensity of said beam in accordance with the characteristics of the optical image and for scanning said beam across said target area to form a raster having an electronic charge pattern that corresponds to said optical image to :be projected,

a layer of substantially uniform thickness disposed on said end wall at the end opposite from said end wall and forming an optical reflecting surface, said layer consisting of an electrostrictive material responsive to the electrical charge thereon to change its thickness as a function of said charge and deform said surface from its normal position,

means for transferring said electron charge pattern from said end wall to said layer to thereby charge said layer similar to said charge pattern on said end wall and thereby change the thickness of said layer corresponding to said optical image,

means for directing light onto said optical reflecting surface so as to be reflected therefrom in accordance with the variations in said thickness, and

an optical system for projecting on said screen at least a portion of the light reflected from said optical surface and deformed by variations in the thickness of the optical surface.

7 55 7. Projection means for projecting an enlarged optical from the source and for use with an external light source image onto a projection screen, including: for obtaining a projection of an image onto an enlarged a projection screen having a surface for displaying a viewing surface of a projection screen in accordance with visual image, the charge characteristics of the charge-producing means, a cathode ray tube having an envelope that defines a an end wall made from a dielectric material and facvolume having a vacuum therein, ing the charge-producing means to accumulate an end wall on one end of said envelope forming a charges at diflerent positions on the end Wall in actarget area, the end wall being made from a dieleccordance with the characteristics of the charges from tric material to accumulate a charge on the end the charge-producing means, wall, 10 a layer of an electrostrictive material disposed in conmeans disposed at the opposite end of said envelope tiguous relationship to the end wall to provide variafor directing a beam of electrons across said volume tions in thickness at different positions in accordance toward said target area to scan said area and create with the charge introduced to the layer at these difan electron charge on said target area that corferent positions, and responds to said optical image to be projected, means operatively coupled to the end wall and to the a layer of electrostrictive material disposed on said end layer of electrostrictive material for introducing the wall at the end opposite from said end wall and charge at the different positions on the end wall to responsive to the electrical charge on said optical the layer of the electrostrictive material. layer to change its thickness as a function of said 9. In the combination set forth in claim 8, the last charge, said layer normally having a substantially mentioned means constituting a plurality of closely spaced uniform thickness and an optical reflecting surface, Wires extending from the end wall to the layer of electromeans for transferring said electron charge pattern from strictive material.

said end wall to said layer of electrostrictive material to thereby charge said layer s milar to said charge Rsffiiemefi {339d y 319 Examine! pattern on said end wall and thereby change the U I gTATES PA N thickness of said layer in accordance with said charge o pattern so that said reflecting surface will be denhauser 135 formed to correspond to said optical image, 10/19,9 A 5 3 means for directing a beam of light onto said optical 3016417 l/lggz an L ast et al 1787.5 reflecting surface so that llght Wlll be reflected there- 3 040 127 6/1962 L from in accordance with said deformations and avm 1787'S 3 072 742 1/1963 Block 178-75 an optical pro ectlng onto said screen system for projecting the light reflected from said deformations FOREIGN PATENTS on the optical surface to form the enlarged optical 51 10/1939 Great Britain image.

8. In combination foruse with a source of video sig- DAVID G, REDINBAUGH, Primary Examiner. nals and with means for producing electrical charges in accordance with the characteristics of the video signals ROY LAKE Examiner 

1. A CATHODE RAY TUBE COMPRISING THE COMBINATION OF AN ENVELOPE HAVING A DIELECTRIC END WALL ADJACENT ONE END THEREOF, AN ELECTRON GUN DISPOSED ADJACENT THE OPPOSITE END OF SAID ENVELOPE FOR DIRECTING A STREAM OF ELECTRONS TOWARD THE INSIDE SURFACE OF SAID END WALL, ELECTROSTRICTIVE MEANS DISPOSED ON THE OUTSIDE SURFAACE OF SAID END WALL TO FORM AN OPTICAL SURFACE AND MEANS FOR CONDUCTING AN ELECTRICAL CHARGE FROM SAID INSIDE SURFACE OF SAID END WALL TO SAID ELECTROSTRICTIVE MEANS THEREBY CAUSING THE SHAPE OF SAID SURFACE TO CHANGE. 